Problems associated with clinical evaluation of antianginal medications

Assessing the efficacy of antianginal medications is not as easy as it might first appear. Many factors, including the protocol, the subjects chosen for study and the physicians conducting the trial, may produce study bias and thereby yield equivocal results. Objectively attempting to quantitate a subjective event such as angina inherently poses many difficulties. The variable nature of anginal episodes makes identification of attacks, or conversely, elimination of such attacks, difficult to assess. In terms of the protocol, it is necessary to determine what indexes will be used as criteria of efficacy, what doses, either standard or maximally tolerated, will be used for study and what measures will be taken to nullify placebo effect. In terms of patient selection, the varying methods of confirming the diagnosis of ischemia and the questions of concurrent illness, compliance and life-style alterations are all factors that can make findings difficult to elucidate. Finally, investigator bias may be introduced into study results because of prestudy prejudice, involvement in data acquisition and interpretation of findings. It is unlikely that any investigator or group of investigators will ever produce a protocol applicable to all types of antianginal medications that will be universally convincing. Conclusions regarding the efficacy of any antianginal medication will undoubtedly continue to be predicated on assessments made by independent investigators using a variety of research protocols, none of which is likely to be perfect.